Electrical apparatus having a static valve system

ABSTRACT

Fluid cooled electrical apparatus having main and standby coolant pumps. The two pumps are arranged to discharge pumped coolant into a common tube. The tube contains two restrictions which increase the velocity head and decrease the pressure head of fluids flowing therethrough. When the standby pump is not operating, the pressure head of the fluid forced through one restriction by the main pump is equal to the pressure head of the fluid at the intake opening of the standby pump, thus no fluid circulation through the standby pump occurs. A similar condition exists at the other restriction when the main pump is not operating and the standby pump is forcing the coolant through the tube. No mechanical check valves are required to prevent coolant circulation through the non-operating pump.

United States Patent 1191 White ELECTRICAL APPARATUS HAVING A STATIC VALVE SYSTEM [75] Inventor: Dale White, Muncie, Ind.

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

[22 Filed: Oct. 31, 1973 211 App]. No.: 411,498

'[521 Us. Cl 165/107, 174/15 R, 336/57 [51] Int. Cl. F28d 15/00, HOlf 27/10 [58] Field of Search 165/107; 336/57; 174/15 R [56] References Cited UNITED STATES PATENTS 3,602,856 8/1971- White 165/107 X Primar.y Examiner-Albert W. Davis, Jr. Attorney, Agent, or Firm-J. R. Hanway Feb. 25,1975

[57] ABSTRACT Fluid cooled electrical apparatus having main and standby coolant pumps. The two pumps are arranged to discharge pumped coolant into a common tube. The tube contains two restrictions which increasethe velocity head and decrease the pressure head of fluids flowing therethrough. When the standby pump is not operating, the pressure head of the fluid forced through one restriction by the main pump is equal to the pressure head of the fluid at the intake opening of the standby pump, thus no fluid circulation through the standby pump occurs. A similar condition exists at the other restriction when the main pump is not operating and the standby pump is forcing the coolant through the tube. No mechanicalcheck valves are required to prevent coolant circulation through the nonoperatingpump.

8 Claims, 5 Drawing Figures FLUID FROM RADIATOR APPARATUS HAVING A STATIC VALVE SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates, in general, to electrical apparatus and, more specifically, to fluid cooled power transformers having standby fluid pumps.

2. Description of the Prior Art Fluid cooled power transformers often have one or more pumps which force the fluid coolant through radiatorswherein some of the heat of the coolant is dissipated. In certain types of transformers, or in particular applications, one or more standby pumps are fixed to the transformer for use if the main pump fails. Switching from the main pump to the standby pump is usually accomplished automatically, often by the use of pressure or flow responsive control devices.

To prevent the circulation of coolant through the non-operating pump and the resulting reduction in the efficiency of the cooling system, it has been common practice to install check valves in the flow paths of the ELECTRIC AL main and standby pumps. Such valves permit the flow of fluid in only one direction, and thereby prevent circulating flow of coolant through the non-operating pump.

Check valves exhibit several disadvantages. They are objectionably noisy since they operate freely and usually include a valve plate which swings open or closed depending on the flow direction. Such valves are susceptible to mechanical failure due to the moving parts contained therein. Additional gasketed surfaces, which I are potential leakage sources, are necessary to properly attach the valves. The space required to mount the valvesadds to the overall size of the cooling system without increasing the efficiency thereof.

Therefore, it is desirable, and it is an object of this invention, to provide an arrangement for bypassing a non-operating coolant pump without using any components containing moving parts.-

SUMMARY oF THE INVENTION There is disclosed herein new and useful electrical apparatus which includes a main coolant pump and a standby or auxiliary coolant pump. The main and standby pumps each have an intake opening which is connected to a channel containing fluid which has been cooled by flowing through a radiator. Each of the pumps has a discharge opening which is connected to a discharge tube. The discharge tube has an outlet opening which permits coolant flowing therethrough to enter the electrical apparatus and cool its components.

Two restrictions are located within the discharge tube. One restriction is positioned between the outlet opening and the main pump. The other restriction is positioned between the outlet opening and the standby pump. When the main pump is operating, coolantis the non-operating main pump. No check valves are required with the arrangement of this invention.

BRIEF DESCRIPTION OF THE DRAWING Further advantages and uses of this invention will become more apparent when considered in view of the following detailed description and drawing, in which:

FIG. I is a view of a transformer partly broken away and constructed according to this invention;

FIG. IA is a schematic representation of a prior art standby pump arrangement;

FIG. 2 is a partial side view, partly in section, of the pump arrangement shown in FIG. 1;

FIG. 3 is a top view, partly in section, taken generally along the line III-III of FIG. 2;

FIG. 3A is an enlarged, broken away view of the circled portion shown in FIG. 3; and

FIG. 4 is a schematic diagram of the pump arrangement shown in FIG. 3 illustrating the operation thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Throughout the following description, similar reference characters refer to similar elements or members in all the figures of the drawing.

Referring now to the drawing, and to FIG. I in particular, there is shown a fluid cooled power transformer 10 constructed according to this invention. The tank 12 contains the core and winding assembly 14 which is submerged in a fluid coolant, such as mineral oil, which fills the tank 12 to the level 16. The tank 12 supports the transformer bushings, such as the bushings l8, and the radiators 20 and 22. The radiator 20 is shown completely in phantom. The radiator 22 is illustrated, partly in. phantom, as an array of tubes 24 which are connected to the side 26 of the tank 12. Normally, more than one such array would be used for the radiator 22, but only one array is illustrated in FIG. 1 in the interest of clarity.

The radiators 20 and22 function in similar manners. Hot fluid enters the openings 26, flows through the radiator 20 where it is cooled, and enters the tank 12 through openings at the bottom of the radiator 20, such as the opening 28. Means for forcing the fluid through the radiators 20 and 22 may be used, such as the pumps 30 and 32 which may be operated to force coolant through the radiator 22. Cooled fluid from the radiator 22, which is collected in a header contained within the tank 12, flows through either the inlet tube 34 or the inlet tube 36, through the appropriate pump 30 or 32, and through the discharge tube 38 to the inside of the tank 12 where it cools the core and winding assembly 14. The pumps 30 and 32 operate independently of the other rather than simultaneously. Thus one pump may be the main operating pump and the other pump may be the standby pump which is used only if the main pump fails.

FIG. 1A illustrates a prior art arrangement for preventing backflow through a non-operating pump. The coolant from the transformer II enters the radiator 13 and flows through either the pump 15 or the pump 17, whichever is operating, and back into the transformer II. The check valves 19 and 21, which are located in the pump flow paths, permit flow in only one direction and thus prevent circulating coolant flow back through the non-operating pump.

, 3 FIG. 2 is a partial side. elevational view of the transformer 10, shown partly in section. A header means or system, including the header 40 and the channel42, di-

the scope of the invention.,Similarly, the intake openings of the pump and the outlet opening 52 of the discharge tube 38 could be located at different vertical positions. I

FIG. 3,is a sectional view taken generally along the line IIIIII of FIG. 2. When the motor 50 is operating,

the pump '30 moves the cooled fluid 44 from the channel 42 to the inside of the tank 12 which contains the core and winding assembly 14. When the motor 50 is not operating, the motor 56 operates to pump the fluid through the opening 58 and out of the opening 52. The

' removal valves 48, 60, and 64 normally are in the open position at all times, regardless of which pump is operating. They are used mainly for removal and replacement of the pumps and would only be closed at that time. i The discharge tube 38 is constructed in such a manner that, when-one pump is not operating, the flow of fluid produced by the other pump does notcause an appreciable flow of fluid through the non-operating pump. This is accomplished without the use of valves by creating astatic pressure condition across the nonoperating pump.

FIG. ,3A is acut-away view of the portion of the dischargetube 38 enclosed bythe circle llIA in FIG. 2. The discharge opening of the pump 30 is connected to the discharge tube branch 68. The discharge opening of 'thep,ump 3 2 is .connectedto the discharge tube branch 70. The fluid flowing through branch 68 enters branch'72 where it travels into the tank 12. Due to the sizeof therestriction 74 formed by the partition .76 and the discharge tube casi'ng78, thefluidpressure developed at region 80 is sufficient to prevent the flow of fluid into the branch 70. A similar result occurs when fluid is flowing from branch 70and the fluid in branch 68 remains static. Various other physical arrangements may be used to provide the restrictions 74 and 84 without departing from the scope of the invention.

Various openings in the pumping system components are connected together in flow communication relationship, such as the opening 46 and the intake opening of the pump 30which is attached to the valve 48. Such openings, while notconnected together directly, are connected in flow communication relationship since the fluid flowing orcontained between the openings does not substantially change pressure or velocity betweenthe two openings.

FIG. 4 is a schematic diagram illustrating the operation of the static standby pump system. Fluid from the radiator is collected in the channel 42. If the pump 30 is operating, and the pump 32 is on standby and not operating, the fluid is pulled into the opening 46, forced through the restriction 74, and out of the opening 52. It is highly desirable to prevent the flow of any of the cooled fluid 44 into the restriction 84 and out of the opening 58 since this merely recirculates the coolant 4 fluid within the channel 42 and does not cool the transformer components.

Bernoullis'equation states the relationship between the dynamic and static conditions of fluid'when at rest or in laminar flow without resistance. Because of the conservation of energy, the sum of the pressure head, or the pressure term in Bernoullis equation, and the velocity head, or the velocity term in the equation, rn'ust remain equal at the same elevation. Therefore, a

pressure'head can be converted to a velocity'head'without'a substantial decrease in energy,'and similarly, a velocity head can be converted to a pressure head.

In FIG. 4, the fluid near the opening 46 has a definite pressure and velocity, The samepressure andvelocity existsfor the fluid near the opening 58. Generally, pumps increase the pressure head of fluids, thus the pump 30 increases the pressure head ofthe fluid 44 in the discharge tube branch 68. This is accomplished without increasing the velocity head if the intake and discharge openings of the pump 30 arethe same size.

The fluid 44.is forced through the restriction 74 and the discharge tube branch 72. I

Since the restriction 74 has a smaller' area than the outlet opening of the pump 30, the velocity head of the fluid 44 is higher at region 80 than at the opening 46, or at the opening 58. Because the energy is conserved, the increase in velocity head is accompanied by a decrease in pressure head. The restriction 74 is properly.

sized to provide a resultant pressure head at the region 80 which is equalto the pressure head at the openings 46 and 58. In general, the restriction 74 is sufficiently small enough to decrease the pressure head of the fluid flowing therethrough by the amount the pressure head of the fluid was increased by the pump 30.

The pressure heads atregion 80 and at the opening 58 are equal, therefore,-no fluid can flow 'through the restriction 84 and" the pump 32. Thus, all of the fluid forced bythe pump 30 enters-the transformer tank for maximum cooling efficiency. The fluid 44 flows through the discharge tube portion 72 which is flared to increase the area of the opening 52 with respect'to the area of the restriction; Thus, the velocity head of the fluid 44 is decreased and the pressure head is in- Since the pressure head at the opening 52 is greaterthan the pressure head at the opening 46, by the amount added by the pump 30, the fluid 44 flows from the opening 52, through the transformer 10 and the radiator 22, to the opening 46.

Similar operation is provided when the pump32 is operating and the pump 30 is on standby, or hasfailed. The dimensionsof the restriction 84 are established from similar criteria as the restriction 74. Assuming that both pumps 30 and 32 have equal capacities, the restrictions 74 and 84 would have the same dimensions.

The novel apparatus of this invention prevents circulation of fluid through the non-operating pump without the use of any mechanical valves. Since numerous changes may be made in the above-described apparatus, and since different embodiments of the invention may be made without departing from the spirit thereof, it is intended that all of the matter contained in the foregoing description, or shown in the accompanying drawing, shall be interpreted as illustrative rather than limiting.

l claim as my invention:

- 1. An enclosure for electrical apparatus, comprising:

a tank containing a fluid coolant; radiator means which is attached to said tank and through which the coolant flows;

header means into which the coolant which flows through said radiator means is directed;

first and second pumps each having an intake opening and a discharge opening, with the intake opening of each pump connected in flow communication relationship with an opening in said header means; and

a discharge tube having a first opening connected in flow communication relationship with the discharge .opening of said first pump, a second opening connected in flow communication relationship with the discharge opening of said second pump, and a third opening located in flow communication relationship with the coolant in said tank;

said discharge tube having a first restriction located between the first opening and the third opening, and a second restriction located between the second opening and the third opening, with the size of the first restriction having adequate dimensions to provide a pressure head at the second restriction, due to fluid which flows through the first restriction when the first pump is operating, which is substantially equal to the pressure head of the fluid at the intake opening of the second pump, and with the size of the second restriction having adequate dimensions to provide a pressure head at the first restriction, due to fluid which flows through the second restriction when the second pump is operating, which is substantially equal to the pressure head of the fluid at the intake opening of the first pump.

2. The enclosure for electrical apparatus of claim 1 wherein the intake openings of the first and second pumps are located at substantially the same vertical position to provide equal elevation heads at the intake openings of the first and second pumps.

3. The enclosure for electrical apparatus of claim 2 wherein the third opening of the discharge tube is located at the same vertical position as the intake openings of the first and second pumps.

4. The enclosure for electrical apparatus of claim 1 wherein the cross-sectional area of the discharge tube is greater at the third opening thereof than at the location of the first restriction to make the velocity head of the fluid at the third opening lower than the velocity head of the fluid at the first restriction.

5. The enclosure for electrical apparatus of claim 1 wherein the fluid leaving the first restriction, when the first pump is operating, flows substantially parallel to the path ofthe fluid leaving the second restriction when the second pump is operating.

6. The enclosure for electrical apparatus of claim 1 wherein the first and second restrictions are located at substantially the same distance from the third opening.

7. The enclosure for electrical apparatus of claim 6 wherein the first and second pumps have substantially identical capacities, and the first and second restrictions have substantially the same cross-sectional area.

8. The enclosure for electrical apparatus of claim 1 wherein the first restriction has a size which lowers the pressure head of the fluid flowing therethrough by an amount substantially equal to the amount the pressure head of theifluid is raised by passing through the first pump when the first pump is operating. 

1. An enclosure for electrical apparatus, comprising: a tank containing a fluid coolant; radiator means which is attached to said tank and through which the coolant flows; header means into which the coolant which flows through said radiator means is directed; first and second pumps each having an intake opening and a discharge opening, with the intake opening of each pump connected in flow communication relationship with an opening in said header means; and a discharge tube having a first opening connected in flow communication relationship with the discharge opening of said first pump, a second opening connected in flow communication relationship with the discharge opening of said second pump, and a third opening located in flow communication relationship with the coolant in said tank; said discharge tube having a first restriction located between the first opening and the third opening, and a second restriction located between the second opening and the third opening, with the size of the first restriction having adequate dimensions to provide a pressure head at the second restriction, due to fluid which flows through the first restriction when the first pump is operating, which is substantially equal to the pressure head of the fluid at the intake opening of the second pump, and with the size of the second restriction having adequAte dimensions to provide a pressure head at the first restriction, due to fluid which flows through the second restriction when the second pump is operating, which is substantially equal to the pressure head of the fluid at the intake opening of the first pump.
 2. The enclosure for electrical apparatus of claim 1 wherein the intake openings of the first and second pumps are located at substantially the same vertical position to provide equal elevation heads at the intake openings of the first and second pumps.
 3. The enclosure for electrical apparatus of claim 2 wherein the third opening of the discharge tube is located at the same vertical position as the intake openings of the first and second pumps.
 4. The enclosure for electrical apparatus of claim 1 wherein the cross-sectional area of the discharge tube is greater at the third opening thereof than at the location of the first restriction to make the velocity head of the fluid at the third opening lower than the velocity head of the fluid at the first restriction.
 5. The enclosure for electrical apparatus of claim 1 wherein the fluid leaving the first restriction, when the first pump is operating, flows substantially parallel to the path of the fluid leaving the second restriction when the second pump is operating.
 6. The enclosure for electrical apparatus of claim 1 wherein the first and second restrictions are located at substantially the same distance from the third opening.
 7. The enclosure for electrical apparatus of claim 6 wherein the first and second pumps have substantially identical capacities, and the first and second restrictions have substantially the same cross-sectional area.
 8. The enclosure for electrical apparatus of claim 1 wherein the first restriction has a size which lowers the pressure head of the fluid flowing therethrough by an amount substantially equal to the amount the pressure head of the fluid is raised by passing through the first pump when the first pump is operating. 